Sub-sea oil and gas processing typically involves high-pressure, high-temperature, and high-volume and throughput processing equipment and systems. Ambient sea conditions can be harsh as they are generally high-pressure and remote from surface operations. Additionally, sub-sea processing systems often have hazardous process fluids and materials, such as petroleum sludge and sand, which results in a need for sub-sea processing systems that are substantially leak-free. Sub-sea processing components and systems can range in size from less than a meter to hundreds of meters. Due in part to the size of the systems and in part to the harsh ambient conditions faced by sub-sea systems, system components can often be difficult to access and retrieve.
Retrievable sensors, such as retrievable pressure and/or temperature sensors, are sensors which can be replaced while process fluids are present in the area in which a sensed condition is to be measured. In some processing systems, retrievable sensors are employed in a variety of configurations, which can include large clusters of components often referred to as sub-sea trees or “christmas” trees. The sensors are often disposed in a flange or bore in a pipe wall to allow for direct measurement of the process fluid. However, such sensors can be extremely difficult to access. To perform repairs or otherwise retrieve and/or replace components of retrievable sensors and other sub-sea systems, existing techniques often require pulling the whole construction to the surface of the water to be repaired on the deck of a ship. Such methods can be costly and require a lengthy stoppage in production while the construction is repaired on the surface. Additionally, known methods of retrieving sub-sea system components such as sensors can place the components at risk for rupture, for example due to the high pressures of process fluids and/or ambient conditions. Alternative and less costly methods can include the use of remotely-operated sub-sea vehicles.
Accordingly, there is a need for a sub-sea sensor assembly that allows for replacement in use without the requirement to open up the pipe wall or suspend the production/process. There is also a need for a sensor assembly that is readily accessible, easily removable, and substantially leak-free.